Generally, automated cartridge systems (ACS) provide a mechanism by which multiple users in a data processing system can have common access to multiple data storage subsystems, such as multiple volume cartridge (MVC) devices. In conventional MVC devices, transfer of data sets generated by remote user computer terminals for storage on a particular cartridge is performed using a first-in-first-out (FIFO) placement of such data sets, or volumes, on the cartridge based on the time a data set is created or transferred.
While processing is made easier, the problem with such FIFO arrangements relate to the inability to efficiently utilize the physical space on the cartridge whenever earlier stored data sets expire before later stored data sets. When this situation occurs, unusable gaps in data storage media of the MVC device are formed between nonexpired volume data sets.
In order to provide some measure of recovery of such unusable gaps, known management arrangements automatically move all nonexpired data volumes on a particular MVC to a second MVC whenever the ratio of the amount of nonexpired data to the total data capacity on a cartridge falls below a predetermined threshold.
While moving nonexpired data volumes allows reclamation of the fragmented and unusable space or gaps on the first MVC, such a solution is not fully satisfactory because each move requires a considerable amount of processing time to complete, and produces additional physical wear on the MVC components. As a result, a need exists for an improved method for reclaiming fragmented space on a MVC which can minimize the frequency of data movement from one MVC to another, and improve overall efficiency in MVC space utilization.